On Thu, Apr 01, 2010 at 05:56:46PM +0200, Peter Zijlstra wrote:> I would much rather we make call_rcu_preempt() available at all times.

srcu is needed only for XPMEM to make the mmu notifier handlerssleepable. Ignore it for now, it can be done later. The locks you'rechanging are always taken _before_ the mmu notifier_range_start andalways after the mmu_notifier_range_end, so srcu can be done later...

It's orthogonal issue, but the moment these locks are sleepable itsimply worth to switch mmu notifiers to srcu to accommodate XPMEM.